Centrifuges



Dec. 5, 1961 D. A. BOYLAND 3,011,696

CENT RRRRR ES 2o .Izz/vezzrtol J.A.Boy 60/17/69 United States PatentOfiflce 3,011,695 Patented Dec. 5, 1961 3,011,696 CENTRIFUGES Donald Arthur Boyland, 24 Sheridan Gardens, Kenton, England Filed July 13, 1948, Ser. No. 38,530 Claims priority, application Great Britain July 23, 1947 8 Claims. (Cl. 233-46) The present invention relates to centrifuges and is concerned with the withdrawal ofgases or vapours therefrom.

In centrifuges operating at high speeds for example for the separation of gases of high molecular weight where the peripheral speed may be of the order of 4x10 cms. per second, the ratio of the pressure of gas at the periphery to that near the centre is very large. Thus, in an evaporative centrifuge, whereas the pressure at the periphery may be of the order of 1000 mm. Hg, the pressure near the axis, where the concentration of the lighter fraction of the fluid is greatest, may be of the order of 0.001 mm. Hg. or less. Difliculty then arises in the withdrawal of the fluid from a region on or near the axis of the rotor at a rate adequate to maintain useful separation of the constituents.

The present invention is concerned with the provision of novel means for facilitating the withdrawal of fluid from the rotors of centrifuges.

According to the present invention, the rotor of a centrifuge has fixed thereto a collecting chamber connected with the interior of the rotor, usually with the axial region thereof, an injector jet arranged to extract fluid from the collecting chamber, an inlet passage for feeding an extracting fluid from an external source to the jet and an outlet passage through which mixture of fluid from the interior of the rotor and the extracting fluid can pass to the outside of the centrifuge.

The invention will be described by way of example with reference to the accompanying drawing in which FIGURE 1 shows in sectional elevation a part of a centrifuge rotor according to the invention, and FIGURE 2 is a view in section along the line IIiI of FGURE 1 to a slightly smaller scale and showing a modified disposition of jets and outlet passage.

In FIGURE 1, the peripheral Wall of the rotor is shown at 10, one end plate is shown at 11, and at 12 is shown the outer part of the wall of an extraction chamber 13 such as is described in the specification of copending application Serial No. v729,600 filed February 19, 1947. As explained in this earlier specification, the lighter fraction of the fluid being centrifuged is collected in the extraction chambers (of which a number is usually provided around the axis) from the axial region of the rotor through apertures 22 and is centrifuged radially outwards. This lighter fraction from the extraction chamber 13 passes through a passage i4 into a collecting chamber 15 in which is a jet 15. A passage 17 connects the jet with an annular passage 18 which may be formed in the driving spindle or damping spigot usually provided in such rotors. The axis of rotation of the rotor is indicated at 19. A second passage 20 constitutes the outlet passage and this connects with a tube 21 in the centre of the annular passage 18. The mouth of the passage 20 facing the jet is suitably shaped. For ease of manufacture the jet 16, and the entry end 23 of tube 20 may be fashioned separately from the solid end plate, and screwed or otherwise fixed in position in the assembly. They preferably have a shape which gives the optimum conditions for the injector action of the gas from the jet 16.

The collecting chamber 15 may be annular and any desired number of jetslo that will provide a balanced system may be provided. The jets are not necessarily,

and will not usually be, arranged opposite the passages 14. The passages 14- will usually be arranged, as indicated in FIGURE 2, at suitable intervals between the jets. Each jet is, of course, arranged opposite to a separate passage 20, the passages 2% all communicating with the passage 21. Moreover each extraction chamber 13 must be provided with at least one passage 14.

In operation an extracting fluid from an external source is pumped at a relatively high pressure through the passages 18 and 17 to the jet 16 and the lighter fraction of the centrifuged fluid is drawn from the collecting chamber 15 and passes with the extracting fluid through the passages 20 and 21, against the action of the centrifugal force, to the outside.

It is not essential that the fluid extracted should, as described, be from a region near the axis of the rotor. It may be desirable, for example, to arrange that the passages 14 in FIGURE 1 at one end of the rotor pass fluid from the axial region and that passages at the oppo site end of the rotor connect with the interior of the rotor radially outside the extraction chamber walls 12. The method of the invention can be applied at both ends. If a fluid to be centrifuged is introduced into the rotor continuously, this arrangement permits continuous withdrawal of a lighter fraction from a passage 1 as shown in FIGURE 1 and of a heavier fraction from a passage connecting with the rotor outside the chamber walls 12.

As shown in FIGURE 2-, it may be desirable to incline the axes of the jets i6 relatively to the radial direction and to curve the outlet passages, indicated by reference 20 in FIGURE 2, in order to take advantage of the dynamic head pressure of the rotating fluid entering the passages 20 from the chamber 15 as the rotational speed of the fluid falls on approaching-the axis 19, and so to reduce the pressure or velocity at the jet. The curvature of the passages 20 is made such that the convex side faces in the direction of rotation as indicated by the arrow 24 in FIGURE 2. Similarly the inlet tubes 17 may be curved in the same direction as passages 2% to assist the supply of extracting fluid to jet 16.

The extracting fluid should be chosen to be readily separable from the lighter fraction from the rotor. It is usually a gas of substantially lower molecular weight than the said lighter fraction. Amongst the advantages of the invention are that the extracting fluid, and possibly also the mixture in the outlet passages 20 and 21, can be at a relatively high pressure and consequently the size of the driving spindle or damping spigot can be relatively small. This is important at high speeds where bearing friction depends upon the diameter of bearings.

It is not necessary that the pressure of the extracting gas should be critically adjusted, so long as it is high enough, since an increase in this pressure does not increase the risk of the extracting gas entering the rotor through the passages 14. Moreover since the pressure of the extracting fluid in the collecting chamber 15 is relatively low there is little risk of difiusion of the extracting fluid back in to the rotor.

I claim:

1. A centrifuge rotor comprising a collecting chamber, a passage connecting said chamber with the interior of said rotor, an injector jet to extract separated fluid from said chamber and positioned to direct an extracting fluid against the action of centrifugal force, an inlet passage to feed said extracting fluid to said jet and an outlet passage for the passage of said fluids having one end facing said jet.

2. A centrifuge rotor comprising an annular collecting chamber co-axial with the axis of rotation of said rotor, a passage connecting said chamber with the interior of said rotor, an injector jet to extract separated fluid from said chamber and extending into said chamber, an inlet 3 passage to feed an extracting fluid to said jet and an outlet passage debouching from said chamber and facing said jet for the passage of a mixture of said fluids.

3. A centrifuge rotor comprising a collecting chamber, a plurality of passages connecting said chamber with the interior of said rotor, a plurality of injector jets spaced circumferentially relatively to said passages and positioned to direct an extracting fluid through said chamber in a direction having at least a component which is radially inward, an outlet passage associated with each of said jets and disposed with its mouth facing said jet and inlet passages for feeding extracting fluid to said jets.

4. A rotor according to claim 3, wherein said outlet passages have portions extending in a smooth curve in planes transverse to the axis of rotation of said rotor from said chamber towards said axis.

5. A rotor according to claim 4, wherein the axes of said jets are inclined relatively to the radial direction and aligned with the centre lines of the adjacent ends of said outlet passages.

6. A rotor according to claim 3, wherein for the purpose of extracting a lighter fraction from a fluid within said rotor the first-named passages connect with the axial region of said rotor.

7. A rotor according to claim 3, wherein said inlet and outlet passages have portions co-axial with the axis of rotation of said rotor to permit introduction and withdrawal of the fluids from the neighbourhood of said axis.

8. A centrifuge rotor comprising an annular collecting chamber co-axial with the axis of rotation of said rotor, a plurality of passages connecting said chamber with the interior of said rotor, a plurality of injector jets to extract separated fluid from said chamber and extending into said chamber in regions thereof which are displaced circumferentially relatively to said passages, inlet passages to feed an extracting fluid to said jets and facing each said jet an outlet passage debouching from said chamber for the passage of a mixture of said fluids.

References Cited in the file of this patent FOREIGN PATENTS 381,913 Great Britain Oct. 13, 1932 

